The present invention relates to furnaces with fluidized beds.
In particular, the invention relates to a furnace of the type comprising a bed of refactory particles and means for supplying a combustible gas and air to the bed so as to enable the combustible gas to burn within the bed and to fluidize the bed.
In a previous heater having a structure of the type indicated above, the combustible gas and the air are introduced separately into the bed whereby these mix only once they have entered the bed. This solution does not achieve complete mixing nor a uniform distribution of the combustible gas and the air within the bed, and consequently does not allow complete combustion of the combustible gas.
In an attempt to obviate this disadvantage, heaters have also been made in which the combustible gas is mixed with the air before being passed into the bed. In this case, however, it is necessary to provide the heater with means for preventing the combustible gases from burning before entering the bed. For this purpose, for example, a plate of porous ceramic material has been used to act as a base for the bed of refractory particles. The main disadvantage of this solution lies in the fact that, in order for the plate of ceramic material to present sufficient resistance to the flow of heat from the bed to the exterior, it must have a much greater thickness than that necessary to allow it to support the weight of the bed. Consequently, the plate presents a fairly high resistance to the flow of the gaseous mixture.